コンパイラ作成（５８） char*型の値を返す関数
今回の目標
引き続きchar*型のサポートを頑張るよ。
// char*型を返す関数の呼び出し char *answer() { // Answer to the Ultimate Question of Life, the Universe, and Everything return "forty-two"; } int main() { puts(answer()); }
今回はchar*型を返す関数だよ。
function
int型しか受け付けなかったのを変更。
# 関数の構文解析 def function() @labelcnt = 0 @lvars = Hash.new @lvarsize = 0; rettype = nil kind, str = @lex.gettoken rettype = "int" if kind == TK::TYPE then rettype = str kind, str = @lex.gettoken end if kind == TK::SYMBOL && str == "*" then rettype += str kind, str = @lex.gettoken end if kind == TK::EOF then return false end if kind != TK::ID then perror "expected identifier" end @funcname = str parametersize = [] kind, str = @lex.gettoken if kind != TK::SYMBOL || str != "(" then perror end # 引数の処理 kind, str = @lex.gettoken loop do if kind == TK::SYMBOL && str == ")" then break end if kind == TK::TYPE then type = str kind, str = @lex.gettoken if kind == TK::SYMBOL && str == "*" then type += str kind, str = @lex.gettoken end if kind != TK::ID then perror "wrong parameter name" end print "para "+str+"\n" if $opt_d size = sizeof type @lvarsize += size parametersize << size if @lvars[str] then perror "redefinition parameter \"" + str +"\"" end @lvars[str] = [type,@lvarsize] else perror end kind, str = @lex.gettoken if kind == TK::SYMBOL && str == "," then kind, str = @lex.gettoken end end codegen ".global "+@funcname codegen @funcname+":" codegen " push rbp" codegen " mov rbp, rsp" # 仮のコードを作成 idx = codegen " sub rsp, xx" # レジスタで渡された引数をスタックの領域に移す n = @lvars.size offset = 0 (0...n).each do |i| offset += parametersize[i] if parametersize[i] == 4 then codegen " mov dword ptr [rbp - #{offset}], #{@regs32[i]}" else codegen " mov qword ptr [rbp - #{offset}], #{@regs64[i]}" end end kind, str = @lex.gettoken # 関数本体の処理 if kind != TK::SYMBOL || str != "{" then perror end kind, str = block codegen ".RET_" + @funcname + ":" # 16の倍数になるように揃える size = (@lvarsize+15) / 16 * 16 # 正しいサイズでコードを生成し置き換える if size != 0 then codechange idx," sub rsp, #{size}" codegen " add rsp, #{size}" else codechange idx,nil end codegen " pop rbp" codegen " ret" if @functions[@funcname] != nil then perror "redefinition of \"" + @funcname + "\"" end @functions[@funcname] = [rettype,[]] p @lvars if $opt_d # デバッグ用 optimize if $opt_O != 0 codeflush @funcname = nil return true end
char**型とかには対応してないよ。いつかサポートしたいけどずっと先の話かも。
codegen_func
ここも返値で型を返すように変更。
# 関数コールのコード生成 def codegen_func operand type = "int" if @numuseregs != 0 then if @numuseregs % 2 == 1 then codegen " sub rsp, 8" end (0...@numuseregs).each do |i| codegen " push #{@regs64[i]}" end end (0...operand.size-2).each do |i| save = @numuseregs @numuseregs = i type = codegen_el operand[i+2] @numuseregs = save if type == "int" codegen " mov #{@regs32[i]}, eax" elsif type == "char*" codegen " mov #{@regs64[i]}, rax" else perror end end codegen " call " + operand[0].str f = @functions[operand[0].str] if f != nil then type = f[0] end if @numuseregs != 0 then (0...@numuseregs).reverse_each do |i| codegen " pop #{@regs64[i]}" end if @numuseregs % 2 == 1 then codegen " add rsp, 8" end end return type end
Hashのfunctionsを参照するようにしたよ。このHashで管理してる関数のデータは今まで全然参照してなかったよ。これ参照するんで関数を前方参照すると問題が生じるよ。この辺はC言語と同じなんだけど、mycはまだ関数宣言できないからちょっと問題だな。関数の情報が無かったときはデフォルトのint型として処理してるよ。こういう場合モダンなコンパイラはワーニングを出してるよね。mycもやった方が良いんだろうな。
コード生成部
codegen_funcが型情報を返すようになったんで、それに対応。
# 式のコード生成（二項演算の左側被演算子） def codegen_elf(operand) type = "int" if operand.kind_of?(Array) then if !operand[0].kind_of?(Array) && operand[0].kind == TK::ID && operand[1].str == "()" then type = codegen_func operand else type = codegen_el operand end elsif operand.kind == TK::NUMBER then codegen " mov eax, " + operand.str elsif operand.kind == TK::ID then v = @lvars[operand.str] if v == nil then perror "undeclared variable \"" + operand.str + "\"" end codegen " mov eax, dword ptr [rbp - " + v[1].to_s + "]" elsif operand.kind == TK::STRING then type = "char*" label = addliteral operand.str codegen " lea rax, "+label else perror end return type end # 式のコード生成（二項演算の右側被演算子） def codegen_els(op, operand, type_l) if op.str == "+" then ostr = "add " elsif op.str == "-" then ostr = "sub " elsif op.str == "*" then ostr = "imul" elsif op.str == "/" then ostr = "idiv" elsif op.str == "==" then ostr = "cmp " elsif op.str == "!=" then ostr = "cmp " elsif op.str == "<" || op.str == "<" || op.str == ">" || op.str == "<=" || op.str == ">=" then ostr = "cmp " else perror "unknown operator \"" + op.str + "\"" end # 右被演算子を評価 type_r = "int" if operand.kind_of?(Array) then if operand[0].size == 2 && operand[0].kind == TK::ID && operand[1].str == "()" then codegen " sub rsp, 8" codegen " push rax" type_r = codegen_func operand codegen " mov r10d, eax" codegen " pop rax" codegen " add rsp, 8" else codegen " sub rsp, 8" codegen " push rax" type_r = codegen_el operand codegen " mov r10d, eax" codegen " pop rax" codegen " add rsp, 8" end str = "r10d" elsif operand.kind == TK::ID then v = @lvars[operand.str] if v == nil then perror "undeclared variable \"" + operand.str + "\"" end type_r = v[0] if type_r == "char*" str = "qword ptr [rbp - " + v[1].to_s + "]" else str = "dword ptr [rbp - " + v[1].to_s + "]" end elsif operand.kind == TK::NUMBER then str = operand.str elsif operand.kind == TK::STRING then type_r = "char*" label = addliteral operand.str codegen " lea r10, "+label str = "r10" else perror end # 型チェック if type_l != type_r then if type_l == "char*" && type_r == "int" then if op.str != "+" && op.str != "-" then perror "mismatched types to binary operation" end elsif type_l == "int" && type_r == "char*" then if op.str != "+" && op.str != "-" then perror "mismatched types to binary operation" end else perror "mismatched types to binary operation" end elsif type_l == "char*" then perror "mismatched types to binary operation" end # 左被演算子と右被演算子とで計算 if op.str == "==" then codegen " " + ostr + " eax, " + str codegen " sete al" codegen " and eax, 1" elsif op.str == "!=" then codegen " " + ostr + " eax, " + str codegen " setne al" codegen " and eax, 1" elsif op.str == "<" then codegen " " + ostr + " eax, " + str codegen " setl al" codegen " and eax, 1" elsif op.str == ">" then codegen " " + ostr + " eax, " + str codegen " setg al" codegen " and eax, 1" elsif op.str == "<=" then codegen " " + ostr + " eax, " + str codegen " setle al" codegen " and eax, 1" elsif op.str == ">=" then codegen " " + ostr + " eax, " + str codegen " setge al" codegen " and eax, 1" elsif op.str == "*" || op.str == "/" then if str != "r10d" then codegen " mov r10d, " + str end codegen " mov r11, rdx" if op.str == "/" then codegen " cdq" end codegen " " + ostr + " r10d" codegen " mov rdx, r11" else if type_l == "char*" && type_r == "int" then if str == op.str then codegen " " + ostr + " rax, " + str elsif str == "r10d" then codegen " movsx r10, r10d" codegen " " + ostr + " rax, r10" else codegen " mov r10d, " + str codegen " movsx r10, r10d" codegen " " + ostr + " rax, r10" end elsif type_l == "int" && type_r == "char*" then codegen " movsx rax, eax" codegen " " + ostr + " rax, " + str type_l = "char*" else codegen " " + ostr + " eax, " + str end end return type_l end
ちゃんと返値を受け取るようにしただけ。
動作テスト
それじゃ行くよ。
~/myc$ myc -d o15.myc
[forty-two]
[forty-two]
{}
[[puts, (), [[answer, ()]]]]
[[puts, (), [[answer, ()]]]]
{}
{"answer"=>["char*", []], "main"=>["int", []]}
~/myc$ ./o15
forty-two
~/myc$ 動いたよ。さて次は何やろうかな。char*型のサポートはちょっと飽きてきたなあ。何か違うことしたい。
